Despite the availability of antibiotics, Hemophilus influenza b remains an important cause of morbidity and mortality in children. This study proposes to characterize human antibodies specific for the major antigen of H. influenza b, polyribosylribitolphosphate (PRP). Using the methodologies of isoelectric focusing and idiotypic analysis, we will assess the heterogeneity of human PRP-specific antibodies. Comparisons will be made between antibody populations obtained from different individuals in order to detect any dominant and/or shared idiotypes and clonotypes. We wish to test the hypothesis that the human response to PRP is pauciclonal and dominated by recurrent or shared idiotypes. These studies may contribute to understanding the age dependence of the response to H. influenza b and serve as a model system for the human response to carbohydrate antigens. Our long term goal is to determine whether network interactions, based upon idiotypic recognition, contribute to the control of B cell expression in the infant and adult.